U.S. patent application number 13/172534 was filed with the patent office on 2013-01-03 for cement retarder and method of using the same.
Invention is credited to William Chrys Scoggins.
Application Number | 20130000904 13/172534 |
Document ID | / |
Family ID | 46229915 |
Filed Date | 2013-01-03 |
United States Patent
Application |
20130000904 |
Kind Code |
A1 |
Scoggins; William Chrys |
January 3, 2013 |
Cement Retarder and Method of Using the Same
Abstract
The reaction product of a polyhydroxy compound and borax is used
as a cement retarder for slurries introduced into a wellbore. The
molar ratio of the polyhydroxy compound to boron, derived from the
borax, is from 1:1 to about 4:1. The polyhydroxy compound may be a
sugar such as a gluconic acid, gluconate or glucoheptonate or a
salt thereof.
Inventors: |
Scoggins; William Chrys;
(Celle, DE) |
Family ID: |
46229915 |
Appl. No.: |
13/172534 |
Filed: |
June 29, 2011 |
Current U.S.
Class: |
166/293 ;
106/823 |
Current CPC
Class: |
C04B 28/02 20130101;
C07F 5/022 20130101; C09K 8/467 20130101; C04B 40/0039 20130101;
C04B 2103/20 20130101; C04B 2103/20 20130101; C04B 14/062 20130101;
C04B 2103/50 20130101; C04B 2103/50 20130101; C04B 2103/46
20130101; C04B 22/0013 20130101; C04B 24/18 20130101; C04B 22/0013
20130101; C04B 24/06 20130101; C04B 14/06 20130101; C04B 24/06
20130101; C04B 22/0013 20130101; C04B 24/06 20130101; C04B
2103/0086 20130101; C04B 24/06 20130101; C04B 28/02 20130101; C04B
40/0039 20130101; C04B 14/06 20130101; C04B 28/02 20130101; C04B
2103/20 20130101; E21B 33/13 20130101; C04B 14/062 20130101; C04B
2103/46 20130101; C04B 22/0013 20130101; C04B 2103/20 20130101;
C04B 22/0013 20130101 |
Class at
Publication: |
166/293 ;
106/823 |
International
Class: |
E21B 33/13 20060101
E21B033/13; C04B 40/06 20060101 C04B040/06 |
Claims
1. (canceled)
2. The cement retarder of claim 30, wherein the borate salts are
principally metaborate salts.
3. The cement retarder of claim 2, wherein the borate salts are
principally sodium metaborate.
4. The cement retarder of claim 30, wherein the disassociated
borate salts are capable of retarding the setting of cement at
temperatures in excess of 400.degree. F.
5. The cement retarder of claim 30, wherein the polyhydroxy
compound is a sugar.
6. The cement retarder of claim 5, wherein the sugar is gluconic
acid, gluconate, glucoheptonate or salts thereof.
7. A method of retarding the set time of a cementitious slurry
introduced into a wellbore, comprising: (a) introducing into the
wellbore a cementitious slurry comprising water, a cement and a
cement retarder, the cement retarder comprising a product derived
from a polyhydroxy compound and borax, the molar ratio of the
polyhydroxy compound to boron, derived from the borax, is from 1:1
to about 4:1; (b) disassociating borate salts and the polyhydroxy
compound from the cement retarder at an elevated temperature; and
(c) allowing the slurry to harden to a solid mass.
8. The method of claim 7, wherein the cement retarder is prepared
in the presence of caustic.
9. The method of claim 7, wherein the polyhydroxy compound is a
sugar or a salt thereof.
10. The method of claim 9, wherein the sugar is gluconic acid,
gluconate or glucoheptonate or a salt thereof.
11. The method of claim 10, wherein the sugar is gluconic acid or a
salt thereof.
12. The method of claim 11, wherein the molar ratio of gluconic
acid or salt to boron, derived from borax, in the disassociated
product of step (b) is 2:1.
13. The method of claim 10, wherein the sugar is the sodium salt of
glucoheptonate.
14. The method of claim 13, wherein the molar ratio of the sodium
salt of glucoheptonate to borate salts in the disassociated product
of step (b) is 1:1.
15. The method of claim 7, wherein the cement retarder further
comprises a lignin sulfonate.
16. The method of claim 15, wherein the lignin sulfonate is a high
temperature lignin sulfonate.
17. The method of claim 15, further comprising a low to moderate
temperature lignin sulfonate.
18. The method of claim 15, wherein the weight ratio of lignin
sulfonate to the product derived from a polyhydroxy compound and
borax is about 2:1.
19. The method of claim 7, wherein the set retarder comprises a
boron/di-glucoheptonate.
20. The method of claim 15, wherein the lignin sulfonate is
selected from the group consisting of sodium lignosulfonate and
calcium sodium lignosulfonate.
21. The method of claim 7, wherein the borate salts and the
polyhydroxy compound disassociated from the cement retarder at
approximately 290.degree. F.
22. The method of claim 7, wherein the borate salts are principally
metaborate salts.
23. The method of claim 22, wherein the borate salts are
principally sodium metaborate.
24. The method of claim 7, wherein the disassociated borate salts
are capable of retarding the setting of cement at temperatures in
excess of 350.degree. F.
25. The method of claim 24, wherein the disassociated borate salts
are capable of retarding the setting of cement at temperatures in
excess of 400.degree. F.
26. A method of cementing within a gas or oil well, comprising:
pumping into the well a cementitious slurry comprising water, a
hydraulic cement and a cement retarder, the cement retarder
comprising a product derived from a sugar or a salt thereof and
borax, the molar ratio of the polyhydroxy compound to boron,
derived from the borax, is from 1:1 to about 4:1; (b)
disassociating borate salts and the sugar or salt thereof from the
cement retarder at approximately 290.degree. F.; and (c) allowing
the slurry to harden to a solid mass.
27. The method of claim 26, wherein the cement retarder is prepared
in the presence of caustic.
28. The method of claim 26, wherein the cement retarder further
comprises a lignin sulfonate.
29. The method of claim 26, wherein the set retarder is selected
from the group consisting of boron/di-gluconate,
boron/mono-glucoheptonate, boron/di-glucoheptonate and
boron/mono-gluconate.
30. A cement retarder derived from a polyhydroxy compound and
borax, the molar ratio of the polyhydroxy compound to boron,
derived from the borax, is from 1:1 to about 4:1, wherein, at
270.degree. F. or above, the cement retarder disassociates and
further wherein the disassociated products are capable of retarding
the setting of cement at temperatures in excess of 350.degree.
F.
31. A method of cementing within a gas or oil well, comprising: (a)
pumping into the well a cementitious slurry comprising water, a
hydraulic cement and a cement retarder, the cement retarder
comprising a complex derived from a polyhydroxy compound and borax,
wherein the molar ratio of the polyhydroxy compound to boron,
derived from the borax, is from 1:1 to about 4:1; (b) breaking down
the complex into disassociated products at temperatures of
270.degree. F. and above; and (c) retarding the setting of cement
until temperatures are in excess of 350.degree. F.
32. The method of claim 31, wherein the cement retarder further
comprises a lignin sulfonate.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a high temperature cement retarder
and to a method of cementing a well with the cement retarder.
BACKGROUND OF THE INVENTION
[0002] Hydraulic cements are cements that set and develop
compressive strength due to a hydration reaction, and thus can be
set under water. Hydraulic cements are often used for cementing
pipes or casings within a wellbore. Successful cementing of well
pipe and casing during oil and gas well completion requires
cementitious slurries to exhibit a pumpable viscosity, good fluid
loss control, minimal settling of particles and the ability to set
within a practical time at elevated temperatures.
[0003] In a typical completion operation, the cementitious slurry
is pumped into the well, down the inside of the pipe or casing and
back up the outside of the pipe or casing through the annular
space. This process seals the subterranean zones (often referred to
as "zonal isolation") in the formation and supports the casing.
Under normal conditions, hydraulic cements, such as Portland
cement, quickly develop compressive strength upon introduction to
the well, typically within 48 hours from introduction. As time
progresses, the cement develops greater strength while hydration
continues.
[0004] It is common to use a retarder with the hydraulic cement in
order to increase the pumping time of the cementitious slurry. In
so doing, the retarder provides adequate thickening time to the
cementitious slurry and thus enables placement of the slurry at its
desired location. In order to minimize lost rig time, the
thickening time of a cementitious slurry to attain a Bearden
consistency (Bc) of 70 is most desirably from about 4 to about 5
hours.
[0005] In general, set retarders may be characterized as being low,
medium or high temperature retarders depending on the bottom hole
temperature encountered. In addition to increasing the pumping time
of the cementitious slurry at elevated temperatures, the retarder
also extends the setting time of the cementitious slurry.
[0006] Water-soluble sugars, sugar acids and their salts, borax and
boric acid are known cement retarders. For instance, U.S. Pat. No.
3,100,526 discloses the use of glucoheptonic acid and salts thereof
as a retarder; U.S. Pat. No. 3,053,673 discloses retarder systems
containing a lignin derivative, such as a lignosulfonic acid salt,
and either gluconic acid, gluconic acid delta lactone or an alkali
metal, ammonium or alkaline earth metal gluconate; U.S. Pat. No.
4,065,318 discloses blends of borax, boric acid and gum arabic as
retarders; U.S. Pat. No. 4,210,455 discloses set retarders of
alkaline earth metal salts of sugar acids as well as alkaline earth
metal salts of borate esters of sugars; and U.S. Pat. No. 4,706,755
discusses the use of borax as cement retarders.
[0007] Sugars have proven to be highly desirable as set retarders
since they are environmentally safe. However, the use of sugars is
restricted to low bottom hole temperatures since they break down at
temperatures in excess of 250.degree. F.
[0008] Boric acid and borax (also known as sodium tetraborate
decahydrate, sodium tetraborate, sodium borate and disodium
tetraborate) are considered high temperature retarders but are
known to over-retard the cementitious slurry at lower temperatures.
A slurry which is over-retarded contains too much retarder and thus
takes a very long time to set. In some cases, an over-retarded
cement slurry will not set at all. A slurry which is over-retarded
increases the costs of cementing, including loss of rig time. For
this reason, boric acid and borax are typically applied at high
temperatures, generally in excess of 350.degree. F.
[0009] In addition to over-retarding the slurry, boric acid and
borax are not highly soluble in water at ambient temperatures.
Thus, when a cementitious slurry is prepared on the fly, there
typically is an abundance of non-dissolved, dispersed particulates
of boric acid and borax in the slurry. When introduced downhole,
shorter or uncontrolled set times and lost rig time are often seen
since setting requires dissolution of the borax or boric acid in
the slurry.
[0010] Further, boric acid set retarders usually contain boric acid
or its equivalent in excess of 5.5%. Such amounts are in excess of
established international thresholds of non-toxicity.
[0011] A need exists for a set retarder which may be applied over a
broad temperature range and which does not over-retard the
cementitious slurry introduced into the well.
[0012] A need further exists for a high temperature cement retarder
which is both environmentally safe and environmentally
friendly.
[0013] Further, a need exists for the development of a high
temperature retarder which delays setting of a cement slurry at
bottom hole temperatures in excess of 350.degree. F.
SUMMARY OF THE INVENTION
[0014] A cement retarder which does not rapidly break down at
temperatures above 250.degree. F. may be formed by reacting a
polyhydroxy compound and borax under controlled conditions. The
polyhydroxy compound and borax forms a "complex" which is defined
by boron being covalently bonded with one or more, preferably four,
oxygens of the hydroxyl groups of the polyhydroxy compound and
borate groups forming ionic bonds with sodium.
[0015] The disassociation temperature of the complex is greater
than the disassociation temperature of the non-complexed
polyhydroxy compound. Within the complex, the molecules of the
polyhydroxy compound are placed into a fixed position by the borate
groups. As the temperature downhole increases, the complex finally
disassociates around 270.degree. F. to render a high temperature
set retarder; the disassociated complex releasing the polyhydroxy
compound and various borate salts. Thus, the borate groups keep the
polyhydroxy compound from breaking down at temperatures less than
270.degree. F. and in turn, the polyhydroxy compound, by forming
ester bonds with the borate groups, prevents these from
over-retarding the slurry at lower temperatures. As such, the
complex provides for the release of various borate salts at highly
elevated temperatures.
[0016] The complex further may be formed in the presence of caustic
or alkali hydroxide under controlled conditions. The sodium
tetraborate in solution then reacts with the hydroxy groups of the
polyhydroxy compound and, in light of the fact that it is a Lewis
acid, links boron with oxygens of the hydroxy groups of the
polyhydroxy compound. The reaction, where the polyhydroxy compounds
are sugars and four oxygens are linked to one boron, may be
represented by any of the following equations:
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+8C.sub.5H.sub.6(OH).sub.5COOH+10NaOH.f-
wdarw.4(C.sub.5H.sub.6(OH).sub.3O.sub.2COONa).sub.2BNa+27H.sub.2O;
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+8C.sub.6H.sub.7(OH).sub.6COONa+2NaOH.f-
wdarw.4(C.sub.6H.sub.7(OH).sub.4O.sub.2COONa).sub.2BNa+19H.sub.2O;
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+4C.sub.6H.sub.7(OH).sub.6COONa+2NaOH.f-
wdarw.4C.sub.6H.sub.7(OH).sub.2O.sub.4COONa BNa+19H.sub.2O; or
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+4C.sub.5H.sub.6(OH).sub.5COOH+6NaOH.fw-
darw.2(C.sub.5H.sub.6(OH)O.sub.4COONa).sub.2B.sub.2Na.sub.2+23H.sub.2O.
[0017] Since the borate salts form firm covalent bonds with the
polyhydroxy compound, it may no longer pose a threat of
over-retardation to the slurry. Further, lost rig time may be
circumvented since dissolution of the borax or boric acid in the
slurry is no longer a concern in light of the formation of the
complex.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more fully understand the drawings referred to
in the detailed description of the present invention, a brief
description of each drawing is presented, in which:
[0019] FIG. 1 shows the linear relationship of a
boron/di-glucoheptonate complex at temperatures up to 375.degree.
F.
[0020] FIG. 2 shows the linear relationship of a
boron/mono-glucoheptonate complex at temperatures up to 410.degree.
F.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The cement set retarder is a borate ester complex formed
from a polyhydroxy compound (low temperature cement retarder) and
borate salts, such as sodium tetraborate (high temperature cement
retarder). The borate ester complex is formed typically in the
presence of an alkaline medium.
[0022] The polyhydroxy component of the complex as well as the
borate portion of the complex are masked at lower temperatures.
Thus, through the formation of borate ester bonds, the borate
portion of the complex prevents the polyhydroxy compound from
breaking down and the polyhydroxy compound prevents the borate from
over-retarding at lower temperatures by keeping borate groups
"fixed" or inactive within the complex. As the temperature to which
the cement slurry is exposed reaches approximately 270.degree. F.,
the complex breaks down, the polyhydroxy compound and the
metaborate are released. The released metaborate may then retard
the setting of the cement up to 350.degree. F. and as high as
410.degree. F. and above.
[0023] In an embodiment, the complex may be prepared by reacting
stoichiometric quantities of borax, an alkali hydroxide and a
polyhydroxy compound. The complex contains covalent bonds, formed
between boron and the oxygens of the hydroxyl groups of the
polyhydroxy compound, as well as ionic bonds, formed by the borate
groups and sodium.
[0024] The molar ratio of hydroxyl groups in the polyhydroxy
compound to boron in the cement retarder (derived from the borax),
is from about 1:1 to about 4:1, though the ratio may be as high as
100:1. In a preferred embodiment, the cement retarder defined
herein may be made by reacting 1 to 2 moles of a polyhydroxy
compound per 1 mole of borax in the presence of caustic to yield a
complex which exhibits excellent cement retarding properties at
temperatures as high as 400.degree. F. and above.
[0025] The polyhydroxy compound may be a sugar, a sugar acid, a
salt of a sugar acid, a glycol, polyvinyl alcohol, hydroxyethyl
cellulose, carboxymethylhydroxyethyl cellulose, a starch, a
galactomannase such as hydroxypropyl guar, or other natural or
synthetic compounds containing multiple hydroxyl groups.
Preferably, the polyhydroxy compounds contains vicinal hydroxy
groups.
[0026] In a preferred embodiment, the polyhydroxy compound is a
sugar. Most preferred are gluconic acid or a salt thereof,
glucoheptonic acid, or a salt thereof. In a preferred embodiment, 4
to 8 moles of sodium glucoheptonate may be reacted with one mole of
borax to yield a complex of the glucoheptonate and sodium
tetraborate. A representative reaction between borax and sodium
glucoheptonate to form a 1:1 dimer of glucoheptonate/borate may be
illustrated as:
##STR00001##
wherein the 1:1 molar ratio borate dimer may be prepared by
reacting 1 mole of borax with 4 moles of sodium glucoheptonate in
water in the presence of caustic. During the reaction, the pH of
the solution drops and an alkaline medium, shown as sodium
hydroxide, is added to increase the pH. Typically, the pH of the
final reactant solution is between from about 8.0 to about 9.0.
During the reaction, two borate groups form firm ester linkages to
the two sugars thus preventing most vibrational, rotational and
translational motion.
[0027] Restrictions on vibrational, rotational and translational
motion are more pronounced when polymeric complexes are formed. For
instance, under controlled reaction conditions 1 mole of borax may
be reacted with 4 moles of sodium glucoheptonate in the presence of
caustic to produce a polymeric complex having a 1:1 molar ratio
between borate and sodium glucoheptonate:
##STR00002##
The polymeric complex may be formed by intra-, as well as,
inter-molecular borate ester linkages and would be more favored for
the 1:1 molar ratio of sugar to borate than the 2:1 ratio.
[0028] The process of elevated heat downhole causes an increase in
various rotational, vibrational and translational motions of the
functional groups of polyhydroxy compounds and their derivatives to
be very rapid until the covalent bonds break. The breaking of the
covalent bonds causes the polyhydroxy compound to lose its physical
and chemical properties. When introduced in a non-complexed form,
the polyhydroxy compound typically thermally degrades at a downhole
temperature around 250.degree. F. or greater. Such degradation is
usually characterized by oxidation, dehydration and various other
condensation reactions of the polyhydroxy compound, initially,
especially between the vicinal --OH groups.
[0029] The cement retarder described herein puts the functional
groups of the molecules of the polyhydroxy compounds into a fixed
position by complexation or crosslinking of the metal borate.
During solvation, the complex becomes surrounded by water
molecules; the borate is then masked and is no longer capable of
retarding the slurry. With an increase in temperature, the kinetic
energy of the complex increases and degrades, thus breaking apart
to form BO.sub.2.sup.- anions (metaborates) in-situ which then
retard the cementitious slurry. Under some experimental conditions,
the molar ratio of polyhydroxy compound to metaborate in the
disassociated product may range from 1:1 to 2:1. For instance, the
molar ratio of sodium glucoheptonate and sodium metaborate in the
disassociated product may be 1:1 to 2:1 and the molar ratio of
gluconic acid or gluconic acid salt to sodium metaborate in the
disassociated product may be 2:1.
[0030] Thermal degradation of the polymeric glucoheptonate/borate
"complex" may be illustrated as:
##STR00003##
wherein at 290.degree. F., the complex has been broken down into
units of sodium glucoheptonate and sodium metaborate. At
temperatures in excess of 290.degree. F., the sugars are thermally
degraded and only sodium metaborate remains.
[0031] Thus, the life expectancy of the sugar molecules increase
dramatically, even at very high temperatures. Along with the
polyhydroxy compound, the other portion of the complex, i.e.,
sodium metaborate, exhibits cement retardation properties. The
breaking of the "complex" at very high temperatures provides for
the release of retarder at very high temperatures.
[0032] The "complex" described herein is particularly advantageous
since it is environmentally friendly. For instance, the components
of the complex have been released for usage in the North Sea.
[0033] Whereas borax per se is considered a more-or-less efficient
high temperature cement retarder, its low solubility in water at
room temperature of only 2.5% restricts its application greatly
since it has to be added as a powder or suspension. When added as a
suspension, its effectiveness is dependent on its rate of
solvation. This causes concern due to the danger of
under-retardation and over-retardation. In addition, the recently
established international threshold of toxicity (Rep. Cat. 2;
R-60-61) for borax indicates that any retarder or blend of
retarders with a borax concentration greater than 8.5 wt. % must be
labeled as being toxic and possibly damaging to the human embryo.
This greatly restricts its application. In contrast, the complex
defined herein is readily soluble in water, readily biodegradable
and non-bioaccumulating as well as non-toxic in the retarder
formulation since the concentration of borax is below 8.5%.
Typically, the retarder formulated with the complex defined herein
contains between 1.80%-3.42% of borax equivalent.
[0034] The complex defined herein is a broad-range retarder and
thus may be applied at a much broader temperature range by, for
instance, changing the quantities of the polyhydroxy compound and
borax. Being a broad-range retarder, the "complex" retards settling
of slurries at temperatures from 200.degree. F. to in excess of
400.degree. F. while showing a linear relationship between the
thickening time (TT) of the slurry and the quantity of composite in
the cementitious slurry. For instance, by changing the dosage of
the retarder in the slurry, it can prolong the setting of cement
slurries at temperatures from 250.degree. F. to about 410.degree.
F.
[0035] The complex is formed typically in the presence of an
alkaline medium. The alkaline medium may be formed from such
caustic as sodium hydroxide, potassium hydroxide, lithium hydroxide
or cesium hydroxide, though typically is sodium hydroxide.
Typically the molar ratio of caustic to sodium tetraborate is from
about 1:1 to about 10:1, preferably from about 1:1 to about 6:1.
This is dependent on whether the sugar acid is added as a salt or
as the free acid.
[0036] The complex may further be used in combination with a
conventional low, moderate or high temperature cement retarder in
order to attain a very broad range cement retarder for low, medium
and high temperatures. When used, the conventional cement retarder
is preferably a low to moderate temperature cement retarder. In a
preferred embodiment, the low to moderate temperature cement
retarder is a lignin sulfonate, such as a sodium lignosulfonate,
calcium lignosulfonate, etc. When present, the weight ratio of
conventional cement retarder to complex is typically from 2 to
about 6. In a preferred embodiment, the conventional cement
retarder is a conventional low to moderate temperature cement
retarder and the complex is the reaction product of sodium
glucoheptonate and sodium tetraborate. Suitable weight ratios
include 2:1, conventional cement retarder to complex.
[0037] The set retarder is used with an aqueous slurry of cement
for introduction into a gas or oil wellbore. Hydraulically-active
cementitious materials, suitable for use in the cementitious
slurry, include materials with hydraulic properties, such as
hydraulic cement, slag and blends of hydraulic cement and slag
(slagment), which are well known in the art. The term "hydraulic
cement" refers to any inorganic cement that hardens or sets due to
hydration. As used herein, the term "hydraulically-active" refers
to properties of a cementitious material that allow the material to
set in a manner like hydraulic cement, either with or without
additional activation. Hydraulically-active cementitious materials
may also have minor amounts of extenders such as bentonite,
gilsonite, and cementitious materials used either without any
appreciable sand or aggregate material or admixed with a granular
filling material such as sand, ground limestone, the like. Strength
enhancers such as silica powder or silica flour can be employed as
well. Hydraulic cements, for instance, include Portland cements,
aluminous cements, pozzolan cements, fly ash cements, magnesia
cements (Sorel cements) and the like. Thus, for example, any of the
oil well type cements of the class "A-H" as listed in the API Spec
10, (1st ed., 1982), are suitable hydraulic cements. In addition,
the cementitious material may include silica sand/flour and/or
weighing agents including hematite or barite.
[0038] Mixing water is utilized with the dry cement composition to
produce a fluid pumpable slurry of suitable consistency. API Spec
10, Second Edition, June 1984 which is known in the cement
industry, describes an approved apparatus and method for measuring
the consistency of cement slurries in terms of Bearden consistency
(Bc). A pumpable slurry should measure in the range from about 2-20
Bc and preferably be in the range from about 5 to 11 Bc. Slurries
thinner than about 5 Bc will tend to have greater particle settling
and free water generation. Slurries thicker than about 20 Bc become
increasingly difficult to mix and pump.
[0039] Depending upon the particular slurry and intended conditions
of use, mixing water is utilized in the slurry of the present
invention in the range from about 30 to 150 weight percent based
upon the dry weight of cement and preferably is in the range of
about 35 to 90 weight percent.
[0040] The cementitious slurry of the invention may further contain
conventional additives used in the cementing of a gas or oil
wellbore such as suspending or thixotropic agents, fluid loss
control additives, strength retrogression additives, permeability
reducers, weighting materials, permeability reducers and
anti-settling agents, etc.
[0041] The set retarders employed in the cementitious slurries of
the invention do not require an intensifier. In fact, the
cementitious slurries typically exhibit retardation of set time at
temperatures in excess of 400.degree. F. If desired, intensifiers
known in the art, such as those disclosed in U.S. Pat. No.
5,105,885, may be employed.
[0042] The set retarder is capable of delaying the set time of the
cementitious composition until the slurry is placed into its
desired location. When used, the set time of the aqueous slurry may
be delayed until downhole temperatures as high as 410.degree. F.
are obtained. Thus, the aqueous slurry may be hardened to a solid
mass at elevated temperatures within the wellbore. Further, the
aqueous slurries used in the invention may exhibit set times at
elevated temperatures even in the absence of an intensifier.
[0043] The following examples are illustrative of some of the
embodiments of the present invention. Other embodiments within the
scope of the claims herein will be apparent to one skilled in the
art from consideration of the description set forth herein. It is
intended that the specification, together with the examples, be
considered exemplary only, with the scope and spirit of the
invention being indicated by the claims which follow.
[0044] All percentages set forth in the Examples are given in terms
of weight units except as may otherwise be indicated.
EXAMPLES
Example 1
[0045] A boron/di-gluconate complex (GLU-1) was prepared by mixing
in a 250 ml flask, equipped with a magnetic stirrer, 200 g (0.51
mol) of gluconic acid solution (50% active) and 24.3 g (0.0637 mol)
borax stirred until clear and left standing overnight. About 24 g
of NaOH was then added and the mixture was allowed to cool. The pH
of the mixture was recorded as 9.0. The density of the complex
solution was 1.34 g/cm.sup.3 and the activity of the complex was
about 48%. The reaction may be represented as:
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+8C.sub.5H.sub.6(OH).sub.5COOH+10NaOH.f-
wdarw.4(C.sub.5H.sub.6(OH).sub.3O.sub.2COONa).sub.2BNa+27H.sub.2O
Example 2
[0046] A boron/di-glucoheptonate complex (GLU-2) was prepared by
mixing in a 250 ml flask, equipped with a magnetic stirrer, 200 g
(0.24 mol) of sodium glucoheptonate solution (30% active) and about
11.5 g (0.0302 mol) borax stirred for about 30 minutes. About 1.7 g
of NaOH was then added and the mixture was stirred for an
additional 5 minutes. The pH of the mixture was recorded as
approximately 8.0. The density of the complex was 1.18 g/cm.sup.3
and the activity of the complex was about 30%. The 2:1 molar
reaction may be represented as:
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+8C.sub.6H.sub.7(OH).sub.6COONa+2NaOH.f-
wdarw.4(C.sub.6H.sub.7(OH).sub.4O.sub.2COONa).sub.2BNa+19H.sub.2O
Example 3
[0047] A boron/mono-glucoheptonate complex (GLU-3) was prepared by
mixing in a 250 ml flask, equipped with a magnetic stirrer, 200 g
(0.24 mol) of sodium glucoheptonate solution (30% active) and about
23.1 g (0.06 mol) borax stirred for about 10 minutes. About 1.7 g
of NaOH was then added and the mixture was stirred for an
additional 5 minutes. The pH of the mixture was recorded as
approximately 8.0. The density of the complex was 1.21 g/cm.sup.3
and the activity of the complex was about 30%. The 1:1 molar
reaction may be represented as:
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+4C.sub.6H.sub.7(OH).sub.6COONa+2NaOH.f-
wdarw.4C.sub.6H.sub.7(OH).sub.2O.sub.4COONa BNa+19H.sub.2O
Example 4
[0048] A boron/mono-gluconate complex (GLU-4) was prepared by
mixing in a 250 ml flask, equipped with a magnetic stirrer, 200 g
(0.51 mol) of gluconic acid solution (50% active) and 48.6 g (0.127
mol) borax stirred for about 5 minutes. About 16.9 g of NaOH was
then added and the mixture was allowed to cool. The pH of the
mixture was recorded as 7.0. The density of the complex was 1.33
g/cm.sup.3 and the activity of the complex was about 47%. The
reaction may be represented as:
Na.sub.2B.sub.4O.sub.7.10H.sub.2O+4C.sub.5H.sub.6(OH).sub.5COOH+6NaOH.fw-
darw.2(C.sub.5H.sub.6(OH)O.sub.4COONa).sub.2B.sub.2Na.sub.2+23H.sub.2O
Examples 5-22
[0049] Cementitious slurries were prepared by mixing neat Class G
Portland cement and fresh water at 14.6 pounds per gallon (ppg). To
each slurry was added at room temperature an amount in gallons per
sack of cement (gps):
[0050] 35% weight percent silica flour;
[0051] 0.1 gps FP-16LP, a defoamer;
[0052] 0.4 gps FL-67LG, a fluid loss control additive;
[0053] 1.2 gps BA-58L, a microsilica suspension bonding agent;
[0054] 0.05 gps ASA-302L, an anti-settling agent; and
[0055] R-15L, a high temperature lignosulfonate cement retarder
wherein FP-16L, FL-67L, BA-58L, ASA-302L, and R-15L are all
products of Baker Hughes Incorporated.
[0056] The resultant slurries were maintained with occasional
agitation. To each slurry was then added GLU-1 or GLU-2.
[0057] Standard API viscosity and fluid loss tests were conducted
on the cement slurries; the viscosity being measured against
industry standard torque measurement of 70/100 Bc (representing the
amount of torque required to move the paddle through the cement
slurry). The results are set forth in Table I. The thickening time
(TT), representing the amount of time (hrs:minutes) that the slurry
remained in a liquid state was then determined. For instance, the
measurement 1:53 refers to the amount of time for the cement slurry
to reach 70/100 Bc. The results are set forth in Table I:
TABLE-US-00001 TABLE I Ex. GLU-1, GLU-2, R-15L, Temp, TT R-15L: No.
Gps gps gps .degree. F. (hrs:mins) GLU-1/2 Comp. 5 0.06 250 1:53
Comp. 6 0.10 250 3:22 Comp. 7 0.12 250 4:07 Comp. 8 0.15 250 11:28
9 0.04 0.12 250 23:01 3 10 0.02 0.12 250 12:06 6 11 0.06 0.12 260
17:26 2 12 0.04 0.12 260 7:04 3 13 0.02 0.12 260 5:16 6 14 0.04
0.14 260 13:29 3.5 15 0.04 0.12 270 3:03 3 16 0.05 0.12 270 4:22
2.4 17 0.07 0.12 270 37:49 1.7 18 0.05 0.14 270 25:23 2.8 19 0.04
0.12 260 8:42 3 20 0.04 0.14 260 12:10 3.5 21 0.04 0.16 260 51:53
4.0 22 0.05 0.12 260 59:36 2.4
Table I illustrates GLU-1 to be an excellent retarder even at very
small additions. GLU-2 rendered better results than GLU-1.
Examples 19-45
[0058] Cementitious slurries were prepared by mixing Class G
Portland cement and fresh water at 14.6 ppg. To each slurry was
added at room temperature 35 weight percent silica flour, 0.01 gps
FP-16L G deformer, 0.40 gps FL-67L, 1.2 gps BA-58L, 0.05 gps
ASA-302L and a mixture of 200 g R-12L and 100 g of GLU-2 (R-12L
X2). (R-12L is a low to moderate temperature lignosulfonate cement
retarder.) The thickening time (TT) data is set forth in Table
II:
TABLE-US-00002 TABLE II Ex. R-12LX2, Temp, TT No. gps .degree. F.
(hrs) 23 0.10 250 3.0 24 0.12 250 3.75 25 0.14 250 4.83 26 0.14 270
2.4 27 0.16 270 2.8 28 0.18 270 3.0 29 0.18 290 8.86 30 0.20 290
12.25 31 0.22 290 16.45 32 0.16 310 3.25 33 0.18 310 4.5 34 0.20
310 5.5 35 0.22 310 6.1 36 0.22 330 3.25 37 0.24 330 4.0 38 0.26
330 4.83 39 0.28 330 5.0 40 0.30 330 5.75 41 0.30 350 3.11 42 0.40
350 6.4 43 0.40 375 4.0 44 0.42 375 4.0 45 0.46 375 4.1
[0059] The data of Table II is plotted in FIG. 1. As illustrated,
at all temperature ranges there was almost a perfect linear
relationship between the thickening time (TT) of the slurry and the
quantity of R-12L-X2 added. Further, FIG. 1 shows that the low to
moderate temperature lignosulfonate retarder starts to break down
as the temperature of the cement retarder system
(lignosulfonate+polymeric glucoheptonate/borate "complex") reaches
270.degree. F. This can be seen by a decrease in thickening time at
this temperature. As the temperature of the system is further
increased, FIG. 1 shows a sudden increase in thickening time at
290.degree. F. from 3 hours to 15 hours which indicates that the
sodium gluconate/borate "complex" became thermally unstable and
started to fall apart forming sodium borate (NaBO.sub.2) and sodium
glucoheptonate (C.sub.7H.sub.13O.sub.8Na) which are both strong
retarders and caused the system to have a much longer thickening
time. Finally, above 290.degree. F. the sodium glucoheptonate
further degraded leaving only the sodium borate as the high
temperature retarder component left in the system. This is
illustrated by the system returning to "normal" thickening times of
approximately 4 hours (and linear quantities of retarder added)
even with increasing temperatures. FIG. 1 shows that the borate
retarder stops working above 375.degree. F. (slope of line
approaching zero) which can be noticed by the slurry not being able
to be retarded much over 4 hours, regardless of how much retarder
was added.
Examples 46-77
[0060] Cementitious slurries were prepared by mixing neat Class G
Portland cement and fresh water at 16.0 ppg. To each slurry was
added at room temperature 0.01 gps FP-16LG, 0.08 gps CD-34L (a
chemical dispersant of Baker Hughes Incorporated) and the
combination of 200 g R-12L and 100 g of GLU-3 (R-12L X2B). A
comparison between R-12-X2 and R-12L-X2B is shown in Table III:
TABLE-US-00003 TABLE III R-12L-X2 R-12L-X2B Temp, 70Bc 70Bc
.degree. F. Gal/sk TT (hrs) TT (hrs) 270 0.18 21.86 10.06 290 0.18
12.96 6.56 310 0.18 5.36 3.25 350 0.4 6.4 6.4
The thickening time (TT) to reach 70 Bc at bottom hole circulating
temperatures (BHCT) is illustrated in Table IV:
TABLE-US-00004 TABLE IV Ex. BHCT TT (HRS:MIN) No. (Deg F.)
R-12L-X2B to 70 Bc 46 250 0.14 3:02 47 250 0.16 4:44 48 250 0.18
6:54 49 270 0.18 2:10 50 270 0.20 2:22 51 270 0.24 3:05 52 270 0.25
3:31 53 270 0.26 10:00 54 270 0.28 15:00 55 290 0.24 2:05 56 290
0.26 4:05 57 290 0.28 6:03 58 310 0.25 4:15 59 310 0.28 4:33 60 310
0.31 7:06 61 330 0.27 2:54 62 330 0.3 4:37 63 330 0.33 6:48 350
0.32 3:57 65 350 0.34 4:27 66 350 0.37 4:39 67 350 0.4 6:25 68 370
0.36 3:24 69 370 0.39 3:45 70 370 0.44 4:23 71 390 0.4 2:53 72 390
0.44 2:59 73 390 0.8 4:38 74 410 0.4 2:11 75 410 0.44 2:18 76 410
0.6 2:47 77 410 0.8 2:58
Table IV illustrates that at temperatures as high as 410.degree. F.
control of the slurry setting remains possible. Further, Table IV
shows that changing the molar ratio of hydroxyl groups:borax from
2:1 to 1:1 reduces the breakdown point of 290.degree. F. to
270.degree. F. but increases the thermal stability of the
glucoheptonate/borate complex up to 410.degree. F. (slope of line
approaches zero) of the complex as shown in FIG. 2. This means that
at 410.degree. F. and above, further retardation is not possible,
regardless of how much retarder is added.
[0061] From the foregoing, it will be observed that numerous
variations and modifications may be effected without departing from
the true spirit and scope of the novel concepts of the
invention.
* * * * *